Devices of this kind are known in which an inertia mass held in an operative position by a spring or a magnet is freed by an acceleration or a deceleration of a predetermined intensity to effect the opening or closing of the electrical contacts. Such devices are usually mounted in a vehicle in a position such that they respond to acceleration or deceleration in a horizontal direction, so that if the vehicle is subject to an impact from the front, the side, or the rear, the electrical contacts are operated. It is a disadvantage of such devices that they may not be capable of being easily reset to their original, unoperated, condition.
An object of this invention is to provide an inertia switch device which mitigates this disadvantage.